High Resolution Mapping of Interstellar Clouds by Near–ir Scattering

We discuss the possibility of mapping interstellar clouds at unprecedentedly high spatial resolution by means of near–IR imaging of their scattered light. We calculate the scattering of the interstellar radiation field by a cloud model obtained from the simulation of a supersonic turbulent flow. Synthetic maps of scattered light are computed in the J, H and K bands and are found to allow an accurate estimate of column density, in the range of visual extinction between 1 and 20 magnitudes. We provide a formalism to convert the intensity of scattered light at these near–IR bands into a total gas column density. We also show that this new method of mapping interstellar clouds is within the capability of existing near–IR facilities, which can achieve a spatial resolution of up to ∼ 0.1 arcsec. This opens new perspectives in the study of interstellar dust and gas structure on very small scales. The validity of the method has been recently demonstrated by the extraordinary images of the Perseus region obtained by Foster & Goodman (2005), which motivated this investigation. Subject headings: ISM: clouds — ISM: structure — scattering — infrared: ISM — radiative transfer —